As for an RF analog LSI, to configure a circuit including high-performance capacitor element, resistor element and inductor element is an important factor. Particularly, the polysilicon resistor element has been conventionally used for the resistor element in a LSI, but the resistance value is fluctuated by the temperature increase due to the heat applied in the package mounting process and the self-heating caused by current flow, which poses a problem in configuring a high-precision analog circuit.
Japanese Patent Application Laid-Open Publication No. 5-275619 (Patent Document 1) discloses a technique of performing an activation annealing of impurities in a polysilicon layer after forming a nitride film covering an upper surface and side surfaces of the polysilicon layer in order to prevent the fluctuation of a resistance value of a polysilicon resistor element due to the oxidation of the polysilicon layer in an activation annealing of impurities ion-implanted into the polysilicon layer.
Also, an important issue for the solution of the above-described problem is to incorporate a metal resistor element of a tantalum nitride (TaN) based material or the like, which has been widely used for a single resistor element, has small frequency dependence of a resistance value and a small resistance-temperature coefficient and is stable against heat generated in the mounting and use, into the miniaturized LSI process.
FIG. 2 shows a metal resistor element described in Japanese Patent Application Laid-Open Publication No. 2004-014769 (Patent Document 2). In the metal resistor element of Patent Document 2, an organic film 8 is formed on a substrate 2 and a curing at 200 to 400° C. is performed, and then, an oxidation preventing layer 15 made of an inorganic material is formed. By this means, the diffusion of oxidative components from the organic film 8 is suppressed, thereby preventing the resistance fluctuation due to the oxidation of a resistive element 3 represented by TaN. Also, the resistive element 3 is integrally formed with the oxidation preventing layer 15 in vacuum. Further, the structure of the resistive element 3 itself is made to have a two-layer structure of a substrate-side low resistance layer 3b and a surface-side high resistance layer 3a, so that the influence of oxidation on the surface side is confined within the surface-side high resistance layer 3a, thereby preventing the influence due to the oxidation from the top and bottom to the substrate-side low resistance layer 3b that actually functions as the resistive element.